1. Field
This invention relates to high temperature electrochemical cells employing molten alkali metal as an electrode-reactant.
2. Prior Art
Various types of electrochemical cells employing molten alkali metal electrode-reactants are known. These cells generally employ an ionically conductive ceramic, e.g., beta"-alumina, or glass membrane through which alkali metal ions pass.
Secondary batteries employing a molten sodium electrode and a molten sulfur electrode are described in U.S. Pat. Nos. 3,404,035 and 3,404,036 to Kummer et al. A primary battery having a molten sodium reactant in contact with a sodium ion conductive ceramic membrane is described in U.S. Pat. No. 3,458,356 to Kummer et al.
These cells experience a higher internal resistance than is generally desired. For example, a secondary battery of the type described in U.S. Pat. Nos. 3,404,035 and 3,404,036, has an electrical resistance across the ceramic membrane corresponding to a specific resistivity of the electrolyte membrane which is generally at least 4 to 5 ohm-cm when the cell is operated at about 300.degree. C. This internal resistance of the membrane diminishes the overall effectiveness and efficiency of the cell.